Supersonic Molecular Beam Sampling System for Mass Spectrometric Studies of High Pressure Flow Systems

Book excerpt: In this paper experiments are preported on beam intensity and mass separation effects for a mass spectrometer sampling system designed for chemically reacting gases at 1,000K and one atmosphere. The coupling between the reacting chamber and the mass spectrometer was achieved by a supersonic molecular beam of the type suggested by Kantrowitz and Grey. The initial expansion was accomplished by a free jet from a continuum sonic orifice. The system was designed to minimize the change in chemical composition of the sampled gas by orifice boundary layer contamination, sample-skimmer interaction, chemical reactions and condensation during the expansion, mass separation and background gas infiltration. Beams from known sources were generated and sampled. The observed beam intensity and composition were compared to those calculated from theory. This paper also provides a compact statement of the present state of the art of molecular beam technology as it applies to sampling, together with enough background material to illustrate the main requirements imposed on molecular beam systems in this application. (Author).